An explicit approximate expression for half-wave potentials of irreversible steady-state current-voltage curves at a microdisk electrode was derived from the diffusion equation and the Butler–Volmer ...equation on the basis of the previous analytical method K. Aoki, K. Tokuda, H. Matsuda, J. Electroanal. Chem. 235 (1987) 87. The plot of the half-wave potential,
E
1/2 against ln(1−
exp(−(
E
1/2−
E
0))
F/RT) showed a linear relation with the slope of
RT/
αF, irrespective of the values of the kinetic parameters, where
a is the radius of the electrode and
α is the transfer coefficient. Values on the both axis in this plot are readily accessible from the voltammograms. The intercept gave the rate constant. Values of kinetic parameters obtained from the disk model were very close to those from the hemisphere model although there is big difference in current distribution on the two model electrodes.
The effect of benzotriazole (BTAH) on the anodic dissolution of copper in 1 M HCl solution was investigated by using a rotating disc electrode (RDE) and a rotating hemispherical electrode (RHSE). It ...was shown that the presence of Cu(I) (CuCl or CuCl
2
−) on the copper surface is necessary to have the inhibitive effect of BTAH. Just below the current plateau, the effect of BTAH depends on the electrode geometry: for the RDE, the electrode surface remained partially active, the protection by BTAH occurred only on a ring at the edge of the electrode, whereas for the RHSE the surface is uniformly covered by a protective BTAH complex. For both electrodes without the presence of BTAH, a surface roughness develops during the copper electrodissolution that can be kinetically interpreted as a porous-like electrode with pores of finite size. In the presence of BTAH and for the RSHE, the size of the pores becomes semi-infinite.
Tafel analysis in practice Li, Danlei; Lin, Chuhong; Batchelor-McAuley, Christopher ...
Journal of electroanalytical chemistry (Lausanne, Switzerland),
10/2018, Letnik:
826
Journal Article
Recenzirano
Voltammetric waves under five different mass-transport regimes (macroelectrode, microdisc, micro-hemisphere, micro-hemicylinder and single microband) for an irreversible one-electron transfer process ...were simulated and analysed to find the appropriate Tafel region for accurate analysis. The transfer coefficient was found to deviate significantly from its true value as a function of potential in all cases due to the influence of mass-transport. If and how a simple analytical mass-transport correction in which the current is corrected for the change in the reactant concentration at the surface can be used to improve the measurement of transfer coefficient was investigated. It is shown that this correction is only rigorously valid for a uniformly accessible microelectrode under a true steady-state condition. This translates to hemispherical electrodes only of the set of five considered. The fraction of the current used in Tafel analysis (Tafel region) can be increased to around 50% for quasi-steady state regimes (hemicylindrical and single band electrodes) with this analytical correction but it completely failed in linear diffusion regimes (macroelectrodes). In the latter case an improved empirical correction is suggested.
•The appropriate parts of a voltammogram for accurate quantitative Tafel analysis are investigated.•Mass-transport regimes considered are macroelectrode, micro-hemisphere, microdisc, micro-hemicylinder and single microband.•An improved empirical mass-transport corrected Tafel analysis is suggested for macroelectrodes (linear diffusion regime).
Artificial intelligence (AI) is used to learn the key voltammetric characteristics of the dissociative CE mechanism via training from multiple simulations using bespoke code. This allows first for ...the prediction of voltammograms without the need for further simulations, given knowledge of the relevant experimental parameters (rate and equilibrium constants, electrode geometry, and diffusion coefficients). Second, it is applied to analyze noisy experimental voltammetry to characterize the mechanistic type and to successfully extract the key kinetic and thermodynamic parameters.
This article is the authors’ last contribution to a trilogy of research papers submitted to Energies’ Special Issue on Electromagnetic Field Computation, aimed at the theoretical analysis and ...numerical computation of the frequency-dependent complex impedance of hemispherical electrodes. In this work, we consider a pair of distant identical hemispherical electrodes buried in the ground, whose constitutive parameters (conductivity and permittivity) are assigned diverse values. Simulation experiments carried out using a full-wave finite element method, considering different combinations of the earth’s constitutive parameters, reveal that the grounding impedance of the electrode system can exhibit surprisingly varied frequency behavior. For frequencies close to zero, the impedance can start out inductive or capacitive, then go through a number of resonant transitions between inductive and capacitive states, finally tending towards purely resistive behavior. The results are interpreted using theoretical approximations valid for low- and high-frequency regimes.
In this study, protein-imprinted sensors with thin bulk films were electrochemically fabricated on gold-coated quartz crystal electrodes with hemispherical porous gold patterns for detecting trypsin ...(Trp). The gold patterns were electrodeposited on a polystyrene colloidal monolayer and then rinsed using toluene. For Trp imprinting on the gold patterned electrodes, a thin layer with a poly(o-phenylenediamine) and Trp protein was formed using a cyclic voltammetry method under optimized conditions. In addition, a two-dimensional molecularly imprinted polymer (2D-MIP) film was prepared on a planar gold electrode under the same conditions to compare to the dependence of Trp selective recognition on three-dimensional (3D) thin MIP structure, and each corresponding nonimprinted polymer film were constructed by electropolymerization, in the absence of Trp template, to compare molecular imprinting effects. The sensing properties of Trp imprinted sensors were investigated using electrochemical, such as cyclic voltammetry and electrochemical impedance spectroscopy, and microgravimetric methods to confirm the sensitivity and selectivity of MIP films. The 3D-MIP films demonstrated a higher imprinting factor (3.51) in 48-μg/mL of Trp concentration than the 2D-MIP film, and the limit of detection was calculated to be 70.9-ng/mL. In addition, the films exhibited higher electrochemical sensing responses due to increased Trp recognition by the effective molecular imprinting over a larger surface area. Thus, the construction of 3D-MIP films for the protein imprinting could provide excellent specificity, faster kinetics, and higher sensitivity for detecting macromolecular proteins than 2D-MIP films.
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•Trypsin-imprinted sensors.•Gold-coated quartz crystal electrodes with hemispherical porous gold patterns.•Electropolymerized poly(o-phenylenediamine) for protein imprinting.•Electrochemical and microgravimetric sensing responses on molecularly imprinted polymers.•High sensitivity and selectivity in detecting trypsin.
Abstract
The unsatisfactory electrochemical performance of Zn metal batteries (ZMBs) caused by uncontrollable Zn dendrite growth and detrimental parasitic reactions has significantly hindered their ...large‐scale applications. Herein, periodic hemispherical structures with a preferential exposure of Cu (100) crystal plane are designed and obtained using facile photolithography, which is followed by wet etching treatment. An exposed zincophilic Cu (100) crystal plane with low nucleation barriers acts as the preferred deposition site to induce homogeneous Zn deposition. Additionally, the periodic hemispherical structure with an enlarged surface area not only suppresses the Zn dendrite growth by reducing the local current density, but also synergistically buffers the volume expansion during the cycling process. As a result, the as‐prepared faceted Cu hemispherical electrodes achieve ultra‐stable Coulombic efficiency of over 99.9% for 1500 cycles at a current density of 5 mA cm
−2
. This work has significant potential for the rational design of dendrite‐free Zn anodes to boost their potential for practical applications.
Hemispherical resonator gyro (HRG) is a high-precision gyro developed on the traditional mechanical gyro and optical gyro. The precise assembly of the resonator and the electrode base is a key ...technology to ensure the working performance of the HRG. In this article, a method for identifying the assembly pose error of HRG with flat electrode is proposed. First, the specific definition and quantitative description of the assembly pose error of the resonator were given, and the mathematical model between the assembly pose error and the equivalent capacitance was established. Then, a finite-element simulation model between assembly pose error and equivalent capacitance was established in COMSOL multiphysics, which verified the mathematical model. In addition, on the basis of the mathematical model, the influence of the assembly error on the equivalent capacitance was explored, and the sensitivity of the assembly movement error and rotation error to the equivalent capacitance was analyzed. Finally, the nonlinear relationship between the equivalent capacitance and the assembly pose error is established based on the support vector regression (SVR) model; therefore, the assembly pose error identification was efficiently and reliably realized. The method establishes the quantitative relationship between the assembly pose error and the equivalent capacitance and realizes the accurate and rapid identification of the assembly pose error, which provides a theoretical basis and realization method for the precise assembly process of the high-precision HRG.
An alternative approach is proposed for the analysis of the low-frequency response of a small hemispheric grounding electrode on the top of a cone-shaped mountain with finite height. This article ...revisits a subject that was treated in three previous articles with an incremental improvement. The geometric profile of the bottom of the cone is theoretically focused. The crucial influence of the terrain profile is reconfirmed in the evaluation of the grounding resistance for an elevated terrain.
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